Optical communications using multiplexed single sideband transmission and heterodyne detection
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a technology of optical fiber communication and heterodyne detection, applied in the field of optical fiber communication, can solve the problems of further intensifying this demand, and limiting the performance and/or utility of current optical fiber systems
Inactive Publication Date: 2002-07-25
XYLON LLC
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Upcoming widespread deployment of new bandwidth-intensive services, such as xDSL, will only further intensify this demand.
However, current optical fiber systems also suffer from drawbacks which limit their performance and/or utility.
As a result, the components may not recombine correctly at the receiver, thus distorting or degrading the original signal.
In fact, at certain frequencies, the dispersive effect may result in destructive interference at the receiver, thus effectively preventing the transmission of signals at these frequencies.
However, the additional equipment results in additional power loss (e.g., insertion loss) as well as in additional cost, and different compensators will be required for different types and lengths of fiber.
Other fiber effects, such as fiber nonlinearities, can similarly degrade performance.
MZMs, however, are inherently nonlinear devices.
As a final example, optical fibers have an inherently large bandwidth available for the transmission of data, but constructing transmitters and receivers which can take advantage of this large bandwidth can be problematic.
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includes two extraction paths 850A and 850B, and a combiner 860. Each extraction path 850 receives the incoming electrical signal 150 and is coupled on the output side to combiner 860.
[0079] Each extraction path 850 processes a different sideband within the electrical signal 150 to recover information signals 140A and 140B, respectively. As an example, extraction path 850A might process the upper sideband 154U; whereas extraction path 850B processes the lower sideband 154L. Both extraction paths 850 may use the same tone (e.g., the optical carrier) in their processing, or they may use different tones. Combiner 860 receives the recovered information signals 140A and 140B and constructively combines them to produce a resultant difference component 140C, which contains the original information signal. The difference components 140A and 140B typically may be phase shifted with respect to each other in order to align their phases before they are combined; the amount of the phase shift ma...
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Abstract
A transmitter subsystem generates an optical signal which contains multiple subbands of information. The subbands have different polarizations. For example, in one approach, two or more optical transmitters generate optical signals which have different polarizations. An optical combiner optically combines the optical signals into a composite optical signal for transmission across an optical fiber. In another approach, a single optical transmitter generates an optical signal with multiple subbands. The polarization of the subbands is varied, for example by using a birefringent crystal. In another aspect of the invention, each optical transmitter generates an optical signal containing both a lower optical sideband and an upper optical sideband (i.e., a double sideband optical signal). An optical filter selects the upper optical sideband of one optical signal and the lower optical sideband of another optical signal to produce a composite optical signal.
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[0001] This application is a continuation-in-part of pending U.S. patent application Ser. No. 09 / 728,373, "Optical Communications System Using Heterodyne Detection", by Ting K. Yee and Peter H. Chang, filed Nov. 28, 2000, which is a continuation-in-part of pending U.S. patent application Ser. No. 09 / 474,659, "Optical Communications System Using Heterodyne Detection", by Ting K. Yee and Peter H. Chang, filed Dec. 29, 1999.[0002] This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60 / 265,251, "Fiber Optic Communications Using Optical Single Sideband Transmission Including using Interleaver Filters and Heterodyne Detection and Apparatus for Impairment Compensation using Nonlinear Phase Conjugation," by Ting K. Yee, et al., filed Jan. 30, 2001.[0003] This application relates to pending U.S. patent application Ser. No. 09 / 746,261, "Wavelength-Locking of Optical Sources," by Shin-Sheng Tamg, et al., filed Dec. 20, 2000.[0004] This application also relates t...
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Inventor YEE, TING K.CHANG, PETER H.TARNG, SHIN-SHENGCUTLER, GREGORY M.YAZHGUR, SLAVALI, JINEWELL, LAURENCE J.COWARD, JAMES F.ROWAN, MICHAEL W.SWENSON, NORMAN L.BASHAW, MATTHEW C.